Remote Real Time Monitor for Elemental Speciation of Air Particulates

Air particulate has been identified as a source of primary and secondary health risks. More than 5000 air particulate monitoring stations have been established in the United States, mostly for measuring the total mass and the size distribution. Real-time monitoring instruments for mass and size distribution are commercially available today. The network of monitoring stations performing chemical composition is smaller. Samples are typically collected on filters which are then transported to laboratories for analysis. This is particularly true for monitoring for monitoring of heavy metal contamination, which is predominately performed using energy dispersive x-ray fluorescence (EDXRF) analysis in laboratories. Even with a high-power (water cooling needed), heavy and expensive lab instrument a long sampling time (24 hours typical) is needed to achieve reasonable detection sensitivity. We propose development of a unique EDXRF system for real-time measurement and monitoring of elemental composition, particularly heavy metal contaminants. The use of innovative x-ray optics in the proposed system enables time-resolved measurements with significant improved detection sensitivity, and achieves such performance in a low-power, compact and automated system. XOS has successfully demonstrated (in Phase I) the performance of the proposed approach by retrofitting the new x-ray optic technology into the existing particulate monitoring system. Even with the non-optimized prototype, a detection limit of 10 to 40 pg/m3 was achieved for Fe, Cu, Zn, Sr, and Br with a 50W x-ray source and eight hour sampling time, it is estimate that this sensitivity was more than two orders of magnitude higher than that of the conventional EDXRF method. The ultimate goal of the Phase II proposal is to develop a prototype system capable of collecting samples and performing composition measurement in a continuous and automatic mode. We expect to achieve the equivalent detection limit of Phase I with 1-hour time resolution for transition elements with a 50-watt system. The system, which can be configured for PM2.5, PM10, or total suspended particulate (TSP), will be packaged as a field deployable instrument with the size, weight, and power consumption similar to those currently deployed in EPA networks, Considering the proposed technology is unique and new, the initial market may be research-oriented. This will provide the opportunity for the PM monitoring community to review the technology and recognize its benefits. Once accepted by the research community we expect systems deploying the technology to be widely distributed both in the United States and internationally.